The present invention relates to a lithography system, and more particularly, it relates to a lithography system having an exposure apparatus for exposing a substrate to project a pattern onto it on which resist is coated, and a substrate processing apparatus connected to the exposure apparatus and adapted to process the substrate.
In a lithography process mainly effected by an exposure apparatus to manufacture semi-conductor elements and the like, resist is coated on a surface of a substrate such as a wafer by a coater, and, after the substrate is transferred, by a conveying system, to the exposure apparatus, where the exposure process is effected, the exposed substrate is further developed by a developer. In this way, a resist pattern is formed on the substrate. Recently, a so-called coater/developer in which the coater and the developer are integrally incorporated has been used mainly.
In conventional techniques, the coater/developer and the exposure apparatus are separately housed in independent chambers and have independent air-conditioners, and the chambers are controlled to achieve optimum processing conditions (air pressure, temperature, humidity and the like).
Recently, there has been a tendency that exposure light has a short wave length to cope with high density and fine arrangement of an integrated circuit, and, thus, DUV (Deep Ultra Violet) light such as excimer laser has been used as the exposure light. In correspondence to this, high sensitivity resist such as chemically amplified resist has been used as the resist relatively widely. The chemically amplified resist is very sensitive to a surrounding chemical environment and is characterized in that it is apt to react with alkaline substances within atmosphere to change its own property. Thus, in the exposure apparatuses and coater/developers using the chemically amplified resist, each chamber is normally provided with a Hepa filter for removing physical dusts and a chemical filter for removing substances (for example, alkaline substances) harmful to the chemically amplified resist.
As clear from the above explanation, in the lithography process using the chemically amplified resist, it is desirable that the chemically amplified resist is not contacted with the open air or atmosphere from when the resist is coated on the substrate to when the development is completed. To this end, the exposure apparatus and the coater/developer are often assembled as an in-line system. When the exposure apparatus and the coater/developer are assembled as the in-line system, since there is a problem that a portion (connecting portion) through which the wafer is transferred between both apparatuses is influenced by the chemical environment, the connecting portion is sealingly enclosed by a cover to provide the same environment as those in the chambers of both apparatuses, while isolating the connecting portion from an external clean room environment.
However, in the in-line system used in the conventional lithography process, the exposure apparatus and the coater/developer are housed in the independent chambers, respectively, and air pressure, temperature and humidity in each chamber are independently controlled by a corresponding air conditioner. Therefore, the difference in pressure, temperature or/and humidity occurs frequently between both apparatuses, with the result that the environments in both chambers which were controlled with high accuracy affects each other to worsen the environments.
For example, in the exposure apparatus, due to the change in pressure caused by introduction of air from the coater/developer, refractive index of air is forced to change to thereby change the projection magnification of a projection optical system, with the result that the magnification control accuracy during the exposure operation is affected by a bad influence or an air fluctuation due to the change of temperature (the temperature fluctuation) occurs. As a result, since measurement error is apt to occur in laser interferometers for measuring the position of the wafer, stepping accuracy and alignment accuracy of a stage are affected by a bad influence. Also if the humidity is changed, since the refractive index is changed, the similar bad influence would occur.
On the other hand, in the coater/developer, while the optimum temperature for development must be maintained, when the air is introduced from the exposure apparatus, the optimum temperature cannot be maintained, whereby developed result would be affected by a bad influence.